Abstract
Human embryo implantation is a critical multistep process consisting of embryo apposition/adhesion, followed by penetration and invasion. Through embryo penetration, the endometrial epithelial cell barrier is disrupted and remodeled by an unknown mechanism. We have previously developed an in vitro model for human embryo implantation employing the human choriocarcinoma cell line JAR and the human endometrial adenocarcinoma cell line Ishikawa. Using this model we have shown that stimulation with ovarian steroid hormones (17β-estradiol and progesterone, E2P4) and suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, enhances the attachment and adhesion of JAR spheroids to Ishikawa. In the present study we showed that the attachment and adhesion of JAR spheroids and treatment with E2P4 or SAHA individually induce the epithelial-mesenchymal transition (EMT) in Ishikawa cells. This was evident by up-regulation of N-cadherin and vimentin, a mesenchymal cell marker, and concomitant down-regulation of E-cadherin in Ishikawa cells. Stimulation with E2P4 or SAHA accelerated Ishikawa cell motility, increased JAR spheroid outgrowth, and enhanced the unique redistribution of N-cadherin, which was most prominent in proximity to the adhered spheroids. Moreover, an N-cadherin functional blocking antibody attenuated all events but not JAR spheroid adhesion. These results collectively provide evidence suggesting that E2P4- and implanting embryo-induced EMT of endometrial epithelial cells may play a pivotal role in the subsequent processes of human embryo implantation with functional control of N-cadherin.
Highlights
Termed the “implantation window” [1,2,3]
Ovarian Steroid Hormones and JAR Spheroid Attachment/ Adhesion Triggered Up-regulation of Vimentin Expression in Ishikawa Cells—To investigate whether the epithelial-mesenchymal transition (EMT) occurred in EECs during human implantation, we employed an in vitro implantation assay (4 –7) using the human EEC line, Ishikawa [4, 15], and spheroids of the human choriocarcinoma cell line JAR as an embryo model
When the treatment groups were compared with the control, significant up-regulation of vimentin in the treated cells adjacent to the spheroid only occurred in Ishikawa cells pretreated with E2P4, but not with suberoylanilide hydroxamic acid (SAHA) (Fig. 1, A and C)
Summary
Termed the “implantation window” [1,2,3]. Human embryonic implantation is a complex, multistep process, during which the embryo first comes into apposition with, and later adheres onto the EEC layer. Ovarian Steroid Hormones and JAR Spheroid Attachment/ Adhesion Triggered Up-regulation of Vimentin Expression in Ishikawa Cells—To investigate whether the EMT occurred in EECs during human implantation, we employed an in vitro implantation assay (4 –7) using the human EEC line, Ishikawa [4, 15], and spheroids of the human choriocarcinoma cell line JAR as an embryo model. Prior to the addition of JAR spheroids, we pretreated Ishikawa cells for 3 days with or without E2P4 or SAHA, a histone deacetylase inhibitor, capable of enhancing implantation [5].
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